Power supply



POWER SUPPLY Filed May 18, 1955 s9 s9 I Mu m s9 s9 -4f 69 10 e9 70 FIG.6. -f:,

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INVENTORS CLARK E. JOHNSON JR. AND WILLIAM O. PEDERSON ATTORNEYS UnitedStates Patent POWER SUPPLY Clark E. Johnson, Jr., White Bear Lake, Mum,and William O. Pederson, Los Angeles, Calif.

Application May 18, 1955, Serial No. 509,159

Claims. (Cl. 321-24) The herein disclosed invention relates to powersupplies and particularly to a power supply for use in operatingminiature electric trains and small direct current electric motors.

An object of the invention resides in providing a power supply in whichpulses of current are used in the starting of the motor and in whichdirect current is used for the propulsion of the motor after the samehas been started.

Another object of the invention resides in providing a power supplyutilizing a transformer having two windings, and in utilizing a fullwave rectifier in association therewith and in causing one section ofthe rectifier to become operative before the other.

Another object of the invention residesin utilizing switch meansincluding two movable switch arms and two groups of contacts, one groupof contacts being connected to certain of the turns of one of the saidwindings and the other group to certain of the turns of the otherwinding, said contacts being arranged so that the contacts of one groupare engaged by its switch arm before the contacts of the other group areengaged by its switch arm.

A feature of the invention resides in forming the contacts by baringportions of the outermost layer of turns of each of said windings.

Other objects of the invention reside in the novel combination andarrangement of parts and in the details of construction hereinafterillustrated and/or described.

In the drawings:

Fig. 1 is a wiring diagram of a power supply illustrating an embodimentof the invention.

Fig. 2 is a plan view of the transformer used with the invention.

Fig. 3 is an elevational view of the transformer shown in Fig. 2.

Figs. 4, 5, 6 and 7 are diagrammatic views showing the performance ofthe power supply.

The transformer used with the invention is shown in detail in Figs. 2and 3 and is indicated by the reference numeral 10. This transformerutilizes a core 11 which is rectangular in form and has four legs 12,13, 14 and 15. This core is constructed in the customary manner by meansof laminations 16 which are stacked as usual and secured together bymeans of bolts 17 and 18. The bolts 17 and 18 pass through a base 19 andthe core 11 is held in position above said base by means of sleeves 21encircling said bolts and engaging the said base and core. The bolts 17have nuts 22 screwed on the same and which clamp the laminationstogether at the locality of the legs 12, 13 and 15. The bolts 18 haveother sleeves 23 encircling the same and extend through a plate 24overlying the core 11. Nuts 25 screwed on the ends of the bolts 18 holdthe portions of the core at the legs 12, 14 and in position and alsohold the plate 24 rigidly supported above said core.

Mounted on the legs 13 and 14 of core 11 are two coils 26 and 27. Thesecoils include primary windings 28 and 29 and secondary windings 31 and32. The

secondary windings 31 and 32 are disposed outermost of the windings 28and 29 and the outermost turns 33 of the winding 31 are bared along anarcuate path 34 to form a plurality of contacts indicated by thereference numeral 35. In a similar manner the outermost turns 36 of thewinding 32 are bared along an arcuate path 37 to form a second group ofcontacts 38. It will be noted that the extent of the path 37 isconsiderably shorter than the extent of the path 34 of the contacts 35for a purpose to be presently described.

Attached to the base 19 and to the plate 24 are bearings 39 and 40 whichrotatably support a shaft 42. This shaft has attached to it a lever 43which has formed on it a boss 44 resting on the plate 24. A set screw 45screwed into the boss 44 holds the lever 43 in position on said shaft. Acollar 46 also mounted on the shaft 42 engages the under side of thebearing 40. The collar 46 has mounted in it a set screw 47 whichsimilarly holds, the collar attached to said shaft. By means of thisconstruction the lever 43 is held from longitudinal movement. A knob 41on the end of the shaft 42 serves to rotate the same.

The lever 43 has two arms 48 and 49 which extend outwardly in oppositedirections. Attached to the ends of these arms are bosses 51 whichslidably receive shanks 52. These shanks have heads 53 at the upper endsof the same which limit their downward movement and contacts 54 at thelower ends of the same and which are adapted to engage the contacts 33and 38 of the windings 31 and 32. Compression coil springs 55 encirclethe shanks 52 and are mounted between the under sides of the arms 48 and49 and the contacts 54 and urge the contacts 54 into engagement with thecontacts 33 and 38. The contacts 54 and the contacts 35 and 38 form aswitch means indicated in its entirety by the reference numeral 60.

The transformer 10 is connected as follows: Primaries 28 and 29 areconnected together by means of a conductor 56 and to two conductors 157and 158 which are connected to a suitable source of alternating current.One end of the secondary 31 is connected to one element 57 of a dry discrectifier 58. The corresponding end of the other secondary winding 32 isconnected by means of a conductor 59 with one element 61 of a dry discrectifier 62. The other elements 50 of the rectifiers 58 and 62 areconnected by means of conductors 63 and 64 to an output terminal 65. Thetwo contacts 54 of the switch means 60 are connected by means ofconductors 66 and 67 to another output terminal 68.

The operation of the invention is as follows: When the lever 43 is movedso that the contact 54 on switch arm 49 just engages any of the firstturns of the winding 31, current flows through the secondary winding 31only and not through the secondary winding 32. Pulses 69 are thenproduced as shown in Fig. 4. These pulses are of low voltage due to thefact that only a few of the turns of the winding 31 are engaged and saidpulses are spaced due to the fact that only half waved rectification isprocured, the winding 32 not being in the circuit. As the lever 43 isadvanced, the voltage of the pulses increases as shown in Fig. 5, stillwith half waved rectification. As such time the pulses give anon-and-olf flow of current to the motor being started which serves togive intermittent starting pulsesto the motor and producing positivestarting of the motor. Were a direct current applied, only one impulsewould be received, and if this impulse was not effective in starting themotor the motor would simply fail to operate. However, where a series ofimpulses are given, the motor is always caused to start. If the firstimpulse is insutlicient one of the succeeding pulses usually producesthe desired result. As soon as the motor starts, the contacts 54 on theswitch arm 48 are moved to engage the contacts 38. Pulses 70 are thenproduced which are 180 degrees out of phase with the pulses 69 and fullwaved rectification commences. At first these pulses are of lessamplitude .as shown in Fig. 6'. When the contacts 54 reach their extremeclock-' wise position as viewed in Fig. 2, all of the turns of bothwindings are connected in the circuit and complete full wavedrectification is procured as disclosed in Fig. 7. This current serves asdirect current for operating the motor and the motor now continues tooperate in the customary manner.

The advantages of the invention are manifest. The

power supply when the switch means is first actuated produces impulseswhich procure positive starting of the motor. The change from half waverectification to full wave rectification is automatically procured bysimply continuing 'to rotate the switch knob. The change from half waveto full wave rectification is gradual. The construction can befabricated at a nominal expense and permits of using a transformer ofmerely sufiicient capacity to operate a motor after the same has beenstarted. The invention combines easy starting with high runningefliciency. Changes in the specific form of the invention, as hereindescribed, may'be' made within'the scope of what is claimed withoutdeparting from the spirit of the invention. Having described theinvention, what is claimed as new and desired to be protected by LettersPatent is:

' 1. A power supply comprising a transformer including a core havingfirst and secondary windings thereon, a first group of contactsconnected to certain of the turns of said first winding, a second groupof contacts connected to certain of the turns of the second winding, arectifier connected to a certain end of each of said windings, saidrectifiers being further connected to a common terminal, switch meansincluding first and second switch arms movable in unison and connectedto another common terminal, the first switch arm being adapted tosuccessively make contact with said first group of contacts and thesecond switch arm with the second group of contacts to increase thevoltage at said terminals as the switch arms are moved in one direction,the contacts of the'firstwinding being arranged to be engaged by thefirst switch arm before the contacts of the second winding becomeengaged with the second switch arm.

2. A power supply comprising a transformer including a core havingfirstand secondary windings thereon, some of the outermost turns of saidfirst winding being bared to form a first group of contacts, some of theoutermost turns of said second winding being bared to form a secondgroup of contacts, a rectifier connected to a certain end of each ofsaid windings, said rectifiers being further connected to a commonterminal, switch means including first and second switch arms movable inunison and connected to another common terminal, the first switch armbeing adapted to successively make contact with said first group ofcontacts and the second switch arm with the second group of contacts toincrease the voltage at said terminal as the switch arms are moved inone direction, the contacts of the first winding being arranged to beengaged by the first switch arm before the contacts of the secondwinding become engaged with the second switch arm.

3. A power supply comprising a transformer including a core havingspaced facing legs, a first secondary winding wound on one of said legs,a second secondary winding wound on the other of said legs, a group ofcontacts connected to certain of the turns of one of said windings,another group of contacts connected to certain of the turns of the otherwinding, a rectifier connected to a certain end of each of saidwindings, said rectifiers being further connected to a common terminal,switch means including first and second switch arms pivoted about anaxis disposed intermediate said legs and movable in unison and connectedto another common terminal, the first switch arm being adaptedtosuccessively make contact with said first group of contacts and thesecond switch arm with the second group of contacts to increase thevoltage of said terminals as the switch arms are rotated in onedirection, the contacts of the first winding being arranged to beengaged by the first switch arm before the contacts of the secondwinding become engaged with the second switch arm.

4. A power supply comprising a transformer including a core havingspaced facing legs, a first secondary winding wound on one of said legs,a second secondary winding wound on the other of said legs, some of theoutermost turns of said first winding being bared to form a first groupof contacts, some of the outermost turns of said second windings beingbeared to form a second group of contacts, said contacts beingsubstantially in the same plane, a switch lever having two armsextending in opposite directions one being engageable with the firstgroup of contacts and the other being engageable with the second groupof contacts, said second group of contacts being disposed so as to beengaged by the first switch arm before the second group of contactsbecome engaged with the second switch arm.

5. In a power supply comprising a transformer including two windingseach producing the same maximum voltage, separate rectifiers connectedto said windings each windinghaving a number of taps, and simultaneouslymovable contactors movable into contact with said taps, said taps beingdisposed so that the contacts of one winding are engaged by thecomplemental contactor prior to the engagement of the other contactswith their complemental contactor to produce half wave rectification,said contacts being disposed so that when the second named contacts arefirst engaged the voltage in-the winding to which they are connected isless than the voltage in the first named winding to produce full waverectification with different voltages for alternate pulses.

References Cited in the file of this patent UNITED STATES PATENTS931,124 Jackson Aug. 17, 1909 1,110,590 Thomas Sept. 15, 1914 2,281,387Sears Apr. 28, 1942

